Answer: 5 Ω.
- A 1 Ω
- B 5 Ω
- C 7 Ω
- D 25 Ω
Correct answer: B. 5 Ω
Explanation: Z = √(R² + X<sub>L</sub>²) = √(9 + 16) = 5 Ω.
In a pure inductor the current lags the voltage by 90° (energy is briefly stored in the magnetic field before current responds); in a pure capacitor the current leads the voltage by 90° (current must flow to build up charge before voltage rises) - the mnemonic "ELI the ICE man" keeps these straight.
Concept context
AC circuits, impedance, LCR series circuit, resonance, transformers, and power factor.